1. Field of the Invention
The present invention relates generally to inspection apparatus and, more particularly, is directed to a bottle bottom inspection apparatus for inspecting a bottom of bottle made of a transparent material such as glass or the like.
2. Description of the Prior Art
Bottles that are made of transparent materials, such as, glass or the like for liquors, beverages, health drinks or medicines, etc., are extensively utilized up to the present time. Among such bottles, there are many cases noted where such bottles used for beer, beverage or liquors are reclaimed after reaching the final consumers, to be recycled. In such cases, the recollected bottles are reshipped after they have been sufficiently treated in the washing process and then refilled with liquids such as beer, etc., at the plant.
These recycled bottles are, however, different to the new bottles, owing to their passing through a complicated circulation that spreads over a long time period, during which time a good number of them become defective bottles that are inadequate for recycling owing to cracks at the mouth, flaws at the body or a variety of foreign matters or particles being entered into the bottles, etc.
Therefore, as a recent trend, empty bottle inspection machines have become popular, which output signals that indicate the discovery of these bottle defects by a combination of an image sensor and an electronic processor.
The items of inspection objects on such conventional empty bottle inspection machines are mainly three portions which are the bottle mouth, bottle body and bottle bottom. Accordingly, the conventional empty bottle inspection machines accomplish the inspection of the inspection objects by separate inspection apparatus that are located at different positions, respectively. Among these objects, the bottle bottom inspection is considered highly important from various reasons.
In other words, during the circulation processing after the liquid inside the bottle, such as beer, has been drunk, there are cases where cigarette butt, or such package cellophane peels, bottle caps or straws, etc. are pressed into the bottle from the bottle mouth, otherwise such foreign particles including the chips due to bottle mouth cracks enter the bottle, there are many cases that such residues are found without being completely removed from the bottle even after being wash-processed at the plants.
Moreover, such foreign particles include opaque foreign particles, or glass chips, tobacco wrapping peels or the like that are transparent foreign particles, as well as many variations of articles that have different kinds of optical characteristics to an extent that it is extremely difficult to make a bottle bottom inspection machine that is able to inspect all of these objects at the same time.
An example of the above-mentioned conventional bottle bottom inspecting apparatus that inspects a bottom of a transparent bottle will be described with reference to a schematic diagram forming FIG. 1.
As FIG. 1 shows, there is shown a bottle 1 as an example of an object to be inspected and of which the bottle bottom is represented by reference numeral 1A. An image sensor 2 which might be a video camera is located above the mouth of the bottle 1. An electronic processor 3 is adapted to process an electrical signal from the image sensor 2 to determine whether the bottle 1 is good or bad. As a light source that is used to enable the image sensor 2 to pickup a foreign particle at the bottle bottom 1A as an image, a lamp 4 and a light diffusion plate 5 of a disk-configuration made of, for example, a frosted glass are placed under the bottle bottom 1A as shown in FIG. 1. In other words, the positional relationship among the bottle 1, the image sensor 2, the lamp 4 and the light diffusion plate 5 is determined as follows. As shown in FIG. 1, the center axis of the bottle 1 is made coincident with an optical axis 0--0 of the image sensor 2, the surface of the light diffusion plate 5 is made normal to the optical axis 0--0 (substantially parallel to the bottle bottom 1A), the diameter of the light diffusion plate 5 is larger than that of the bottle bottom 1A, and the center of the light diffusion plate 5 is substantially on the optical axis 0--0. Thus, the lamp 4 irradiates the bottle bottom 1A upwardly only through the light diffusion plate 5. Accordingly, the light diffusion plate 5 functions as a planar second lighting plate (light source) for the bottle bottom 1A so that the image sensor 2 may pick up an image of the light diffusion plate 5 as a bright background (or bright field) having uniform brightness relative to the bottle bottom 1A. Thus, when on the bottle bottom 1A there is an opaque or translucent foreign particle, the image sensor 2 picks up the opaque foreign particle as a dark shade in the above bright background (or bright field). Then, on the basis of the picked-up video signal from the image sensor 2, the electronic processor 3 produces a signal indicating the existence of the opaque foreign particle on the bottle bottom 1A.
According to the conventional bottle bottom inspection apparatus as described above, if the foreign particles on the bottle bottom 1A are dark objects, opaque objects or half transparent objects, it is easy for the image sensor 2 to detect the foreign particles by picking up them as dark shades in the bright background of the bottle bottom 1A. If on the other hand the foreign particles are transparent ones such as glass chips, cellophane or the like, the light from the light diffusion plate 5 almost pass through the transparent foreign particles so that they cannot be picked up as dark shades by the image sensor 2. Even when they are picked up as shades by the image sensor 2, they are too faint to be detected by the image sensor 2.